HOW THE USE OF A NEXT-GENERATION 3D CAD TOOL IN BASIC DESIGN STAGE
LEVERAGES TO IMPROVE THE OVERALL WARSHIP DESIGN AND PRODUCTION
Verónica Alonso, SENER, Madrid/Spain, veronica.alonso@sener.es
Carlos Gonzalez, SENER, Madrid/Spain, carlos.gonzalez@sener.es
Rodrigo Perez, SENER, Madrid/Spain, rodrigo.fernandez@sener.es
SUMMARY
At early design stages is where most part of the decisions and costs are compromised, and where 2D drawings are still
widely used. The idea of using a single tool for the whole process, starting with the creation of a 3D model at early
design stages has been profusely required in naval shipbuilding. It is not easy to convince the agents involved about the
advantage of having an increased work at early phases although that will be largely reused downstreams.
This paper describes in detail about the benefit of changing the process of minor warships design, by means of using an
advanced CAD tool from the early stages, describing how it will be an advantage in terms of quality and costs. The most
remarkable benefits are the data integrity and the avoidance of long design periods and cost increases due to errors, rework and inconsistencies.
The main challenges refer to the integration of all stages and disciplines thanks to the use of a single CAD tool that must
be effective at all stages, including those in basic design such us the quick definition of the 3D model as well as in the
transfer of a simplified model to the analysis and calculation tools.
This paper describes SENER findings in minor warships, as an example of engineering work, by means of an approach
based on the use of FORAN, a shipbuilding oriented CAD System.
NOMENCLATURE
CAD
CS
FEA
FEM
LR
1.
Computer Aided Design
Classification Societies
Finite Element Analysis
Finite Element Method
Lloyd´s Register



INTRODUCTION
The definition of a ship project in shipbuilding usually
comprises three stages, conceptual, initial/basic and
detail design (see figure 1). During the detail design
stage the use of a ship 3D model is very common, while
the basic design is still based on 2D drawings in many
companies, although it is the stage where most of the
costs are compromised which implies long design
periods, repetition of relevant parts of the work in
subsequent stages and a potential for multiple design
inconsistencies. This all leads to a major increase in costs
and a low production performance.
Being aware of this situation and also due to marketing
and commercial reasons 3D tools have been introduced
recently in the initial design stage. In some way, the
problem could be understood as another episode of the
traditional debate between the 2D and 3D approaches.
The ship design process is often shared between several
design actors that develop different aspects of the
engineering. The process is rather sequential as the input
for some stages is the output from previous ones. A non
exhaustive list of tasks normally includes:
 Development of the main hull structure based in 2D
drawings.
 These drawings are sent to Classification Societies
(CS) for further analysis and subsequent approval.

In order to check the structure, CS often develop a
3D Model of the structure, based in the 2D drawings
received.
Indeterminate iterations of the process usually arise,
due to the implementation of the comments from the
CS into the 2D drawings.
Detail design activities start once the structure has
been approved, taking as starting point the 2D
drawings to generate a 3D model that will be used
for the early activities in machinery and outfitting.
Additionally, there are other reasons to generate
different 3D models like the needs for special
calculations (finite elements analysis, noise,
vibrations, etc) as well as the requirements for more
realistic (rendered) views of the accommodation
spaces.
Figure 1: Design stages
As an alternative to the traditional method, a new
approach is emerging in shipbuilding. It is based on the
generation of an early ship 3D model during the basic
design stage, by using the same tool as in the detail and
production phases. Although at first sight the detail
design process might seem more complicated, in the long
run the advantages are huge mainly derived from the
reuse of information. As a fundamental requirement for
the solution to be efficient, the generation of the
classification drawings for approval should be simple, as
well as the transference of the model to the analysis tools.
2.
PHILOSOPHY AND PRINCIPLES OF THE
FORAN SOLUTION
This paper focuses on the approach based in FORAN
System and describes the experience of SENER, a
company that plays the double role of software developer
and ship design agent, in the development of tools for the
definition of a ship 3D model in the early design stages,
to be used during basic and detail design and production
phases too.
The proposed solution is based on a 3D ship product
model in which the geometry and the attributes of the
elements of the ship are stored. The model is built as an
essential part of the engineering work, can be visualized
at all stages and can be exploited to obtain information
for material procurement and for production. The main
characteristics of the ship product model are discussed in
the following paragraphs.
Building and early 3D model in FORAN allows to
improve the design process of the ship and to study
different design alternatives in shorter periods of time,
which reduces both delivery schedule and cost. As a
result, it is possible to reach a better performance when
developing the design and, at the same time, to obtain a
product of high quality in a very competitive way. The
FORAN solution is based on the integration of all the
design stages and disciplines, thanks to a single database,
which moreover permits the implementation of
collaborative engineering and guarantees the information
integrity.
The definition of the model is easy, thanks to the
advanced functions implemented in FORAN. The use of
a topological model instead of a geometrical model,
facilitates its definition, allows the quick study of
different design alternatives and simplifies the
modifications, which are very common in the early
design stages. The main advantage of the topological
definition, where geometrical data are not stored but
calculated on-line, is that changes in the main hull
surfaces are automatically incorporated in the modified
elements, just by reprocessing them. In addition, the
topological definition allows the existence of powerful
copy commands making thus the definition far more
efficient than working only with geometry. Another
benefit of the topological model is the size of information
stored in the database, much less than for geometrical
models.
The key aspect of the design process is the definition of a
single ship 3D model, accessible for several designers
working concurrently, to be used in all stages of the
design. While the project is progressing, the level of
detail is increasing and the different parts of the model
are subdivided by means of a progressive top-down
definition. The solution delivered by FORAN includes
tools that facilitate the direct transition from basic to
detail design, by means of simple operations that include
blocks splitting, the assignment of parts to blocks and the
completion of the model with attributes for the
manufacturing phase.
3.
MODELLING SEQUENCE
The modelling sequence in FORAN begins with the
definition of the material catalogues describing plates
and profiles to be used in the design. Once the hull forms,
decks, bulkheads and other surfaces are created, the hull
structure module is used to create the major openings in
all surfaces, the scantling of the main surfaces for plates
and profiles as well as the main structural elements
(floors, web frames, girders, stringers, etc.). The
definition is usually based in the frame and longitudinal
systems which allows a full recalculation of the model in
case of changes in the spacing between elements.
In early stages, plates and profiles are created as objects
representing zones of a surface with common scantling
properties. Therefore, the size of the objects is not
consistent with the manufacturability, which will be
considered in later stages of the design. Other properties
like the continuity and watertightness attributes of
surfaces or parts of them can be defined at any time.
The sequence of the definition of the model in FORAN
has a high degree of flexibility being possible to create
both plates and profiles at any time. However, designers
would normally follow the same rules as when working
in 2D, which means to start with the definition of the
continuous elements because this will allow the
automatic splitting of the non-continuous elements.
The assembly break down to unit or block is optional at
this stage, and the level of detail of the 3D model is the
one required by the classification drawings, with respect
to the type of parts included (brackets, face bars, clips,
collars, etc.) as well as to other characteristics (profile
end cuts, scallops, notches, etc).
4.
SURFACES
Ship moulded surfaces model includes the external hull
form, decks, bulkheads, appendages and superstructures.
Under FORAN, the geometrical representation for all the
surfaces is a collection of trimmed NURBS patches,
Bezier patches, ruled surfaces and implicit surfaces
(planes, cylinders, spheres and cones). The surfaces can
be imported from files using different generic formats,
such as iges and the AP-216 of the step format.
FORAN has two complementary tools for surface
definition. The traditional tool permits the definition of
the hull surface, either conventional or special forms,
such as non-symmetrical ones, multi-hull and offshore
platforms. This tool includes advanced fitting and fairing
options and allows several transformations of the hull
forms (based in block coefficient, longitudinal position
of the centre of buoyancy or quadratic) and other
operations like lengthening or shortening of a ship that
can be easily performed.
FORAN has incorporated recently an additional tool
based in the latest-generation of mechanical design that
can be used for improving hull forms. A target driven
deformation improves the design creativity and the final
shape quality, by means of the use of parametric design
and global surface modelling, as it appears in figure 2.
Figure 2: Different views of the external surface of a ship
5.
HULL
CAPABILITIES
STRUCTURE
3D
MODEL
The intensive use of topology makes possible the
automatic recalculation of all elements when a
modification is performed in upper level concepts (hull
and decks surfaces or material standards). This type of
topological definition produces important time savings
during the development of the basic design, where the
modifications are frequent.
5.1
SHELL AND DECKS
This 3D curved surfaces context allows the definition of
plates, profiles and holes. Work division is made by
using the surface and zone concepts, which allows the
multi-user access to any surface. A general zone may be
used to contain the entities common to several zones.
The following type of profiles can be defined:
 Shell and deck longitudinal.
 Frames and deck beams.
 General profiles.
Profile definition is mainly based on topological
references to already existing structural elements, as well
as to auxiliary concepts used in the early stage of the
design (longitudinal spacing, frame system, other
profiles, etc.). The user can easily assign different
attributes such as material, scantling and web and
thickness orientation., These basic attributes can be
completed by adding constructive attributes (parametric
web, flange end cuts, etc) at any time of the design
process . The profiles can be split up in profile parts later,
when the transition from basic to detailed design is
performed. Profiles crossing other profiles will
automatically generate the necessary cut-outs and
scallops.
All types of profiles including flat, curved and twisted
are represented as solids. Web, flange and the
corresponding end cuts are displayed with a user
configurable degree of accuracy.
Due to the intensive use of topology, the definition of the
shell and deck plating can start in the early stages of the
design, even with a preliminary definition of the hull and
decks. In this regard, the basic concepts are:
 Butts: Lines lying on a surface used as aft and fore
limits for the plates. Butts can have any shape or be
located in transverse planes at any abscissa.
 Seams: Lines lying on a surface used as lower and
upper limits for plates, with any geometric shape.
Seams are usually defined by means of a set of
points on the surface and some additional rules to
define the layout.
 Plates: zones of the surface defined by aft and fore
butts, and lower and upper seams, with attributes
such as gross material, thickness and, optionally,
bevelling/edge preparation, construction margins and
shrinkage factors. Plates can also be the result of
breaking down an existing plate in two smaller
plates.
Flat and curved plates are represented as solids
(including thickness) and the information for plate predevelopment is automatically generated allowing thus an
early material take-off list.
5.2
INTERNAL STRUCTURE
The internal structure context is based on the same high
performance topological and visualization environment
of the curved surfaces, but applied to a section lying on a
plane. This environment provides a set of advanced
functions for the easy definition and modification of
plates (flat, flanged and corrugated), straight and curved
stiffeners, holes, face bars, standard plates, on and off
plane brackets, collars and others.
As an example, you can see in figure 3 a basic design
patrol vessel created using the FHULL.
Figure 3: 3D model of one of the minor warship blocks
created for this paper
It is possible to have several sections in memory making
easy operations, like copy or multiple editions of
elements in different sections. The work division is made
by using the section, structural element and zone
concepts, which allows multi-user access to any section.
The main features are:
 Predefined best practices support through the use of
structural element concept, defining default
constructive values and parameters for plates,
profiles and face bars.
 Automatic part splitting, using the crossing/not
crossing structural element attribute.
 High productivity tools, like one click plate
definition, reduction to the minimum of the auxiliary
geometry and join and split functions for plates and
profiles.
 XML based high performance topological definition
language for the definition of plates, profiles and
face bars.
 Profile and face bars definition using standard
profile cross-sections, parametric cut-outs and
parametric web and flange end cuts.
 Automatic cut-outs insertion for both plates and
profiles.
 Standard or free shape hole definition and automatic
application to the affected plates.
 High productivity commands including split, multiedit and multi-copy for both plates and profiles in
the same or in different sections and structural
elements.
6.
OUTPUT FROM THE 3D MODEL
The next paragraphs describe the tangible outputs
derived from an early hull structure 3D model like
drawings, reports and models to be used in the analysis
and calculation tools. In addition, there are other
important outputs, in fact the existence of a 3D model
makes more efficient the tasks related to the outfitting
basic design as it is explained in point 8 of the paper
Advantages of an early 3D model.
6.1
MAIN
OUTPUT:
DRAWINGS FOR APPROVAL
electrical and accommodation). The drawing generation
is completely user configurable, as the final aspect of the
drawings depends on the user requirements. Drawings
are generated directly from the 3D product model, and
the 2D entities that represent the product model are
linked to the 3D elements, and are always updated with
the latest version of the product model. A symbolic
representation for modelled elements is possible and
different visualization methods are available.
The drawing generation module includes also a function
to reprocess the drawing after changes in the model, and
at the same time keeping any manual modifications
introduced by the user in the drawing. There are also
options for automatic dimensioning and labelling by
means of user-configurable formats and templates
representing different attributes of the selected elements
(identification, scantling, profile cross sections, end-cuts
and others). These entities are also linked to the product
model elements. The drawings generated are compatible
with most of the standard drawing formats too.
6.2
LINK WITH FINITE ELEMENT TOOLS
One of the most relevant aspects during the basic
engineering of a ship is the structural analysis by means
of the application of the finite elements method (FEM),
which makes possible to improve and validate the
feasibility of the design. In practice, it is a laborious task
that requires the preparation of a suitable model for
calculation, meshing, the application of loads and
constraints, processing, post-processing and analysis of
the results.
Most of the finite element tools include standard formats
for the direct import of 3D CAD models, but they fail
when these models come from the shipbuilding industry
due to the complexity of the ship models. The effort
required in the manual simplification of the model
(model cleaning process in the figure 4) is such that it is
more efficient to repeat the model with a calculationoriented approach, which slows down the analysis
process dramatically.
CLASSIFICATION
Although the approach described in this paper is more
general, any improvement in the process of basic design
must consider the fact that the main output during the
hull structure basic design stage is to obtain the
classification drawings for approval. Classification
drawings are symbolic drawings of different types, like:
 Shell and deck drawings (different views, including
expansion).
 Typical planar sections.
 Other detail drawings.
The drawing generation in FORAN is managed by a
single module, which covers the output drawings of all
design disciplines (general, hull structure, outfitting,
Figure 4: Meshing workflow
The use of a ship model already created in a 3D CAD for
FEM analysis would optimise the design performance in
the early stages. For this, there must be an efficient link
between both tools so that a simplified ship model
adapted to each type of calculation can be exported
directly from CAD.
SENER's approach to this problem combines its broad
experience in the development of a CAD/CAM
shipbuilding tool with innovative solutions to obtain the
expected results: a link that makes possible to export a
simplified ship model, leveraging its topological
characteristics. Functional algorithms in FORAN allow
the creation of an intelligent model, simplifying, filtering
and deleting unnecessary data to guarantee the quality of
the model transferred.
Among other functionalities, the user can decide in
FORAN:
 Whether the plates are translated as surfaces by the
neutral axis or the moulded line.
 The automatic assignment of colours to every
material and profile scantling.
 Whether the profiles will be translated as surfaces or
as curves.
 The minimum area to discard the transfer of holes
and brackets.
All structure entities will be subject to an idealization
process aiming to simplify the 3D model, see figure 5, by
using the following criteria:
 For plates, notches, scallops, fillets and chamfers
will be removed from the outer contour.
 For profiles (either via surfaces or curves), notches,
scallops, macro-holes, end-cuts and profile
extensions will be removed.
 Surfaces created as plate or profiles are extended
topologically to the moulded line/neutral axis of the
surface used in its definition. This simplification is
applied on every intersection line with other surfaces
used in the plate or profile definition.
 Plates are splitted in different surfaces using the
profile layout and any other marking line.
 Corrugated and flanged plates are splitted in planar
faces.
 Surfaces sewing, every two surfaces created by a
previous one split will be sewn on the join line.
 Profiles sewing: If the profile is translated as a
surface, flange and web will be sewn. Translated
profile web surface will be sewn to its underlying
plate surface too.
 Plate limits are extended to the surfaces used in its
definition.
Figure 5: FORAN FEM-Link Overview
6.3
OTHER OUTPUTS
One of the advantages inherent to integrated 3D
applications refers to the easiness of data extraction as
the whole product model is stored on a single source of
information. With FORAN, different types of reports that
can be generated are configurable and can be exported to
most of the standard formats like Excel, HTML and
ASCII. Fixed contents reports like steel order (plates and
profiles) and configurable bill of materials can be
obtained based on query conditions decided by the user.
Report contents will depend on the degree of definition
of the project.
Among others, the following reports can be obtained in
FORAN:
 Weight and centre of gravity.
 Painted areas.
 Material takes off.
 Bill of materials, see example below in figure 6.
 Welding lengths.
Figure 6: Example of a bill of materials
7.
TRANSITION TO DETAIL DESIGN
THROUGH THE REUSE OF THE INFORMATION
The key point to for any software solution aiming to
provide a complete solution for ship design and
manufacturing is the capability to provide smooth
transition between the stages of the design avoiding
rework and delays. Thus, as a logical continuation of the
basic design, FORAN provides tools for subdividing and
joining plates and profiles, and also features additional
attributes for detail design such as bevelling, construction
margins and shrinkage factors, and also for defining parts
that are not relevant during the basic design stages.
The way from the initial to the basic and the detailed
design is also the way from the conceptual and abstract
to the concrete and manufacturable. Large conceptual
parts useful to analyze for instance weight and structural
behaviour must be converted in manufacturable parts
reusing all the information provided in the conceptual
stages and detailing when necessary. The split concept is
basic in this transition, for example large longitudinal
layouts are splitted into manufacturable profile parts
inheriting layout attributes and with the appropriated split
properties according to end-cuts, margins, etc. The split
concept is applied to any kind of part, from bulkhead
profiles to curved hull plates.
The level of detail not only concerns geometry but also
attributes. Part attributes irrelevant in conceptual stages
become critical in detailed design. In order to provide a
smooth transition, tools to modify, check and copy
attributes of large groups of pieces are provided.
The block subdivision is perhaps one of the most critical
points in ship design regarding the transition between
design stages. Although split and refinement tools can be
used for block subdivision, some specific tools are
provided in order to perform automatic recalculation of
parts when the block butts are modified. Assignment of
parts to units can be done at any time by means of a
powerful graphical selection tool.
Finally, in this stage it is the right time to complete the
detail design by defining those parts which are not
relevant for the basic design stage.
8.
ADVANTAGES
MODEL
OF
AN
EARLY
3D
It is well known that most of the costs of a ship are
compromised during the initial design stages. The
proposed solution delivers tangible benefits as it
optimizes the process by reducing the time dedicated to
design and consequently the cost. Main advantages can
be summarized as follows:
 Shorter evaluation of different design alternatives
due to the high level of topology that allows an
automatic recalculation in case of upper level
modifications.
 More accurate design due to the use of a 3D tool.
 Less risk of inconsistencies comparing to the 2D
approach in which every view is independent and
has no relation with the others. Instead, the 3D
approach combines the implicit intelligence
associated to the model by means of certain
attributes (continuity, watertightness) with the
graphical checking performed by the user leading to
a design with better quality.
 Easier link with analysis and calculation tools based
in the existence of a single 3D model that, for the
purpose of other calculations, is subject to an
idealization process for easier management in the
FEM/FEA tools.
 Early estimation of materials and weights, including
welding and painting.
 Easier co-ordination among disciplines as hull
structure and various disciplines of outfitting are
represented in the same underlying product model.
This has obvious advantages in terms of interference
or collision checks and leads to a better outfitting
design regarding the general arrangement definition
and critical compartments layout.

9.
Due to the incremental development of the model as
the design evolves, there is a seamless transition to
detail design based in the reuse of data.
MINOR WARSHIP DESIGN
A minor warship design has been defined for this
congress, as an example of engineering work, using
FORAN. It has been decided to explain how was defined
the 3D FORAN model and later on export to this 3D
model to FEM analysis.
9.1
3D FORAN MODEL
The use of the FORAN system for classification projects
allows for the generation of the classification drawings in
an automatic way from the preliminary definition of the
3D model. This then avoids the needs for manual
drawing of the structure in the classification stage.
The benefits using FORAN in this minor warship are:
 3D design.
 More accurate.
 No errors policy.
 Avoiding any interference.
 Better design quality.
 Single database.
 Easier coordination tasks.
 Integration of all disciplines.
 Simultaneous access for users.
 Guarantee the consistency of the information.
 Control of information integrity and access
authorizations.
Topological design implicates better management of the
modifications and shorter evaluation of different design
alternatives. The reuse of the information is covering the
whole design process.
The main characteristics for the minor warship are:
 Work in 3D environment.
 Make a top-down definition of the ship entities.
 Create a topological model to facilitate changes.
 Reuse of the information in detail design.
 Estimate work contents and cost of different tasks.
 Compare design alternatives and predict results.
The FORAN solution is based on several factors, as for
example the main outputs of the basic design are the
Classification drawings for approval. The main use of
FORAN in areas where 3D definition is more efficient,
in areas where drawings generation is more efficient,
shell and decks (plates and profiles) and partial use of the
internal structure (section drawings). The structure
modelling is another factor with the surfaces definition,
the parametric decks and bulkheads surfaces, with
topological reference to the hull, the openings, hatches,
man-holes, doors, etc; plates of zones with common
scantling, profiles of scantling and the main internal
structure elements as girders, web-frames, floors,
stringers, etc.
There are different types of drawings: shell and decks
drawings and section drawings; different type of reports:
weight and centre of gravity, painting surface, welding
information and material order.
One of the main advantages in the basic design using
FORAN is the reuse of the information, the natural
continuation of the basic design, the definitive assembly
breakdown and the additional attributes for detail design.
As example of this, as in the minor warship designed has
been raised: bevelling, construction margins, shrinkage
factors and to define the parts not relevant for the basic
design.
The basic design can be handled by using the concept of
design structural zone:
 The concept of design structural zone is a
hierarchical concept.
 The design structural zone shares common design
rules which simplify the work.
The assembly block is an optional attribute when
generating the parts. This allows a better handling of
panels and profiles.
9.2
FINITE ELEMENT MODEL
One of the most relevant aspects during the basic
engineering of a ship is the structural analysis by means
of the application of the finite elements method (FEM),
which makes possible to improve and validate the
feasibility of the design. In practice, it is a laborious task
that requires the preparation of a suitable model for
calculation, meshing, the application of loads and
constraints, processing, post-processing and analysis of
the results.
In figure 7 it is possible visualize the FEM geometry
exported from one of the minor warship blocks.
Figure 7: FEM geometry in the warship mid block
studied
Most of the finite element tools include standard formats
for the direct import of 3D CAD models, but they fail
when these models come from the shipbuilding industry
due to the complexity of the ship models. The effort
required in the manual simplification of the model is
such that it is more efficient to repeat the model with a
calculation-oriented approach, which slows down the
analysis process dramatically.
The use of a ship model already created in a 3D CAD for
FEM analysis would optimise the design performance in
the early stages. For this, there must be an efficient link
between both tools so that a simplified ship model
adapted to each type of calculation can be exported
directly from CAD.
SENER's approach to this problem combines its broad
experience in the development of a CAD/CAM
shipbuilding tool with innovative solutions to obtain the
expected results: a link that makes possible to export a
simplified ship model, leveraging its topological
characteristics. Functional algorithms in FORAN allow
the creation of an intelligent model, simplifying, filtering
and deleting unnecessary data to guarantee the quality of
the model transferred.
Among other functionalities, the user can decide in
FORAN:
 Whether the plates are translated as surfaces by the
neutral axis or the moulded line
 The automatic assignment of colours to every
material and profile scantling
 Whether the profiles will be translated as surfaces or
as curves
 The minimum area to discard the transfer of holes
and brackets
All structure entities will be subject to an idealization
process aiming to simplify the 3D model by using the
following criteria:
 For plates, notches, scallops, fillets and chamfers
will be removed from the outer contour
 For profiles (either via surfaces or curves), notches,
scallops, macro-holes, end-cuts and profile
extensions will be removed
 Surfaces created as plate or profiles are extended
topologically to the moulded line/neutral axis of the
surface used in its definition. This simplification is
applied on every intersection line with other surfaces
used in the plate or profile definition
 Plates are splitted in different surfaces using the
profile layout and any other marking line
 Corrugated and flanged plates are splitted in planar
faces
 Surfaces sewing, every two surfaces created by a
previous one split will be sewn on the join line
 Profiles sewing: If the profile is translated as a
surface, flange and web will be sewn. Translated
profile web surface will be sewn to its underlying
plate surface too
 Plate limits are extended to the surfaces used in its
definition
When defining a ship model it is possible to take full
advantage of FORAN topology to obtain a good result
when exporting it to FEM. In order to obtain a good
quality of the exported model can be significantly
improved saving a lot of time and work when preparing
the input for FEA analyzers. It should be considered that
most of these tips are oriented to the exportation of an
initial design model. At this stage all the features offered
by topology can help in the creation of a correct
simplified 3D model.
As a consequence, this document has no references to
margins, preparations, assembly marks, shrinkage factors
or building strategy cuts. The final goal is to obtain an
exported FEM model where parts are modelled without
thickness and positioned on the moulded line and all
contacts and intersections are preserved.
9.2.3. Modelling profiles with set-back in the minor
warship vessel
When defining a profile to end with a set-back from a
surface (i.e. a stiffener of a bulkhead ending on a deck
and having a set-back) always should be use the distance
functionality. This way, when exporting to FEM the
profile will be extended up to the reference surface used
in its definition.
9.2.4. Modelling profiles ending on other profiles/plates
in the minor warship vessel
In this project, we have used the profile point in the
definition when modelling profiles ending on other
intersected profiles. This will cause the profiles to be
extended if modelling the intersected profile as bars.
9.2.1. Modelling notches in the minor warship vessel
In the minor warship project, automatic notches have
been used, editing manually some of them. In this
project, we have avoided using auxiliary geometry of any
type. Always use, for the definition of plate contours, the
intersection lines created by the other surfaces instead of
using accident/thickness or auxiliary lines.
9.2.2. Modelling brackets in the minor warship vessel
Use as much as possible standard and macro plates and
the specific commands to insert brackets and macro
brackets. For the creation, select profile's end points to
obtain a correct topological relation.
Figure 9: 2D Finite Element model produced using
FORAN FEM-link, to check scantlings and optimize
structure
In particular cases a displacement between the profile
and the profile point might be needed. To obtain such
result and preserve the topology of the profile point and
set a flange displacement, it is possible to use the
opposite option in the point selection of the profile
creation.
Finally, in the particular case of a profile ending on an
intersected plate always use plate's accident point to
define the profile. The resulting behaviour will be similar
to the previously described cases.
Figure 8: Structure constructed further than the detail
normally required by LR Class for their approval
In this project, we have avoided creating any standard
plate (brackets, collars...) using auxiliary geometry or
creating auxiliary surfaces by profile. Some collar plates
have been created using auxiliary geometry, so we must
take into account the fact that FHULL will not delete
them when exporting to FEM hence, to avoid overlapped
plates, these collars have to be manually deleted with an
external editor.
A collar laying on a curved surface can be either
modelled as a plate using standard geometry or as a
macro plate. In both cases, it will have to be manually
deleted from the exported FEM model.
9.1.5. Modelling Plates in the minor warship vessel
When, in this project, creating plates with a thickness
displacement, we have avoided creating a shifted surface
to place them. We´ve always used the available thickness
orientation possibilities (partially in/out, distance from
moulded in/out). When exporting, every plate/profile
cuts all the contacting plates dividing the resulting
surface. This division is done using the theoretical
FHULL surface. Creating extra surfaces can lead to a
duplication of cuts and fragmentation of the resulting
surfaces.
To create notches, fillets, chamfers on plate's corners, it
is available specific functionality. If, because of the
position or geometry, it is not possible to create them,
postpone the creation to a second phase (after the FEM
analysis). In any case try to avoid creating them using
auxiliary geometry because they won’t be discounted
from the model and they will have to be deleted
manually after exporting.
10.
CONCLUSIONS
FORAN improves design quality, provides higher
precision and reduces the risk of inconsistencies. The
rapid evaluation of several design alternatives and the
early estimation of materials, weights, welding and
painting are additional advantages, in addition with the
efficient link with finite element analysis tools. Finally, it
also facilitates the definition of the outfitting (general
layout and layout of critical compartments) and improves
the coordination between disciplines. In conclusion, the
key points are the simple transition to detail design and
the reuse of information.
This substantial change in the development of the basic
design stage, which is now being required and
implemented, is expected to become the routine way of
working in the future, particularly when the continuation
with the detail design is considered and/or outfitting
design is part of the scope of work.
11.
REFERENCES
1. M Aarnio, ‘Early 3-D Ship Models Enables New
Design Principles and Simulations’, 1st Int. Conf.
Computer and IT Appl. Maritime Ind. (COMPIT),
Potsdam 2000
2. A Rodriguez, M Vivo, A Vinacua, ‘New Tools for
Hull Surface Modelling’, 1st Int. Conf. Computer and IT
Appl. Maritime Ind. (COMPIT), Potsdam 2000
3. L Solano, I Gurrea, P Brunet, ‘Topological Constraints
in Ship Design, ‘From Knowledge Intensive CAD to
Knowledge Intensive Engineering’. U Cuggini and MJ
Wozny (Eds.). Kluwer Academic Publ. 2002
4. L Garcia, V Fernandez, J Torroja, ‘The Role of
CAD/CAE/CAM in Engineering for Production’, ICCAS,
Bremen 1994
12.
AUTHORS’ BIOGRAPHIES
Veronica Alonso holds the current position of Marketing
and Area Manager at SENER. She is responsible for
FORAN commercial activities in North America.
Carlos Gonzalez holds the current position of Area
Sales Manager at SENER. He is responsible for FORAN
commercial activities in the naval sector.
Rodrigo Perez holds the current position of FORAN &
PLM Consultant at SENER.